On Wed, Feb 10, 2021 at 11:44 AM Peter Luschny <[email protected]> wrote:
>
> The compositional inverse (with respect to x) of
>
>     y(t, x) = x - t*(exp(x) - 1)
>
> is
>
>     1/(1-t)*y + t/(1-t)^3*y^2/2! + (t+2*t^2)/(1-t)^5*y^3/3! + 
> (t+8*t^2+6*t^3)/(1-t)^7*y^4/4! + ...
>
> Apparently multivariate power series rings do not know how
> to reverse a series.
>
> Perhaps there is a workaround?

one can try to see if working with univariate series over R(t) will
give the needed inverse.


> Thanks!
>
>
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